Fast cold quench oil for metals

ABSTRACT

A QUENCH OIL OF HIGH QUENCHING SPEED PARTICULARLY USEFUL FOR THE QUENCHING OF STEEL COMPRISES A MAJOR PROPORTION OF A HYDROCARBON OIL OF LUBRICATING OIL VISCOSITY RANGE AND A MINOR PROPORTION OF A PETROLEUM HYDROCARBON RESIN THAT HAS BEEN TREATED WITH A FINE DISPERSION OF METALLIC SODIUM OR REALTED ALKALI METAL.

United States Patent U.S. Cl. 148-29 5 Claims ABSTRACT OF THE DISCLOSUREA quench oil of high quenching speed particularly useful for thequenching of steel comprises a major proportion of a hydrocarbon oil oflubricating oil viscosity range and a minor proportion of a petroleumhydrocarbon resin that has been treated with a fine dispersion ofmetallic sodium or related alkali metal.

BACKGROUND OF THE INVENTION This invention concerns an improved highspeed quenching oil composition for use in the heat treatment of metals,particularl ferrous metals such as steel. The invention also concernsimprovements in the method of quenching metals with the improvedcomposition of the lnvention.

Many metal alloys, particularly ferrous alloys and carbon steels,require heat treatment to develop the desired degrees of hardness andstrength. The basic heat treatments are generally hardening by quenchingand softening by annealing. The hardness of an alloy is mainly dependentupon the formation of a certain physical structure. In the case ofsteel, for example, it is desirable to form martensite in the steel. Thehard martensite structure is particularly suited for such metal parts asgears. To increase the hardness of metal alloys such as steel they areheated to an elevated temperature; for example, above 1600 F. and thenplunged into a comparatively cool quenching medium. In some cases thedesired structure can be obtained immediately, but in other cases themetals are quenched to maximum hardness and then tempered to achieve thedesired hardness and ductility.

In the heat treatment of steel the term quenching covers the process ofcooling the steel from the temperature range at which austenite (solidsolution of carbon in gamma iron) is formed to a temperature below thecritical temperature, which is around 1000 F. If the steel is cooled tooslowly, the austenite is transformed into the softer pearlite. If thecooling is sufliciently rapid, however, the harder martensite is formedinstead. Quenching that is effective in forming martensite is frequentlreferred to as marquenching.

The quenching problem is basically one of heat trans fer. While watercan be used for rapid quenching, it is undesirable in most instances,because it tends to cool the metal too quickly and often results indistortion and cracking. Hydrocarbon oils, and particularly mineraloils, are commonly used as quenching liquids, but unmodified straightmineral oils do not usually form satisfactory quenching media, since theinitial rate of cooling is too slow. Hence, the development of thequench oil art has been in the direction of modifying hydrocarbon oilsby incorporating certain additives therein. See for example U.S. Pats.3,027,315; 3,113,054; 3,159,510 and 3,205,100.

3,681,150 Patented Aug. 1, 1972 ice A particularly eifective quench oilknown to the prior art comprises a major proportion of a hydrocarbonlubricating oil and a minor proportion of a petroleum hydrocarbon resin.Such resins are naturally occurring in paraffin base or Pennsylvaniatype oils, and are obtained therefrom by solvent precipitation, e.g.with propane. Such resins are distinguished from the resins that areobtained by polymerizing steam cracked naphtha streams. The petroleumresins utilized in the present invention are obtained by treating aresidual fraction of a paraffinic crude oil such as a Pennsylvania crudeoil with an excess of liquid propane or related light hydrocarbon underpressure at ambient temperatures. One common procedure for obtainingsuch resins has included the steps of dissolving one volume ofPennsylvania reduced crude in about two volumes of liquid propane,cooling the solution by evaporating some of the propane, removingparaffin war: that is thereby caused to separate from the oil, addingfurther propane up to about 10 volumes per volume of oil, and mildlyheating the solution under pressure. This causes the precipitation of aresinous product of high molecular weight in the form of a heavy viscousmaterial of dark color having a viscosity of about 1,000 SUS at 210 F.This resinous product per se is well known in the prior art. While theprecise composition of such petroleum resin is not fully known it is anessentially neutral product substantially free of acidic material. Seefor example, U.S. Pat. 2,614,991.

Fairly satisfactory quenching oils have been prepared in the prior artby adding from 1 to 10% by weight of such petroleum resins to a lowviscosity hydrocarbon base oil. One such prior art composition hasconsisted of about 5 wt. percent of a hydrocarbon resin of about 2800SUS viscosity at 210 F. in a refined lubricating oil having a viscosityof about 35 to 38 SUS at 210 F. In some applications of this compositionthe quenching speed has not been sufficiently high to be entirelysatisfactory. The quenching speed can be increased slightly by employmgresins of higher viscosity. This adds to the cost of the compositionsince the higher viscosity resins demand a higher price than the lowerviscosity resins. Moreover, the improvement in quenching speed throughthe use of this expedient is minimal, being in the order of 1 second atbest.

DESCRIPTION OF THE INVENTION In accordance with the present invention ithas been found that the ability of a petroleum resin to increase thequenching speed of a quench oil base stock can be improved by treatingthe resin with a fine dispersion of an alkali metal, which can bepotassium or lithium but is preferably sodium because of its lower cost.

The amount of alkali metal that is used to treat the petroleum resinwill range from about 0.2 to about 5 wt. percent, or more usually fromabout 0.3 to about 3 vvt. percent based on the resin. For example,desirable products are obtained by treating a resin with about 1% to 1.5wt. percent of sodium. It is simply necessary to disperse the finelydivided alkali metal in the somewhat warmed resin with the aid of ahomogenizer or equally efiective equipment and then heat the mixture toabout 250 to 450 F. for from about /2 to 4 hours, for example at 300 F.for from about 30 minutes to 2 hours. Alternatively, the finely dividedalkali metal can be dispersed in a portion of the base oil that is to beused for making the quench oil, after which the required amount of themixture of metal and base oil is added to the resin and theabove-described procedure is continued.

The petroleum resin employed in the present invention will be a resinousmaterial having a viscosity in the range of about 1000 to 10,000 SUS at210 F. and preferably a viscosity of from about 2500 to 5000 SUS at 210F. The resin is of the type that is obtained by propane precipitationfrom a Pennsylvania type paraflinic petroleum oil residue, as discussedabove.

The lubricating oil which forms the major component of the quench oil ispreferably a refined mineral lubricating oil having a viscosity in therange of from about 50 to 2000 SUS at 100 F., usually about 100 to 1000SUS at 100 F. Viscosities at 210 F. of the base oil will be in the rangeof about 30 to 100 SUS. Preferably the initial boiling point of the oilshould be at least 600 F. The quench oil composition will comprise thebase oil containing from about 1 to about 10% by weight of the treatedresin.

The nature of this invention and the advantages gained from its practicewill be more clearly understood when reference is made to the followingexamples, which include a preferred embodiment.

Example 1 A petroleum resin obtained by propane precipitation from aresiduum of a Pennsylvania crude oil was employed for this example. Theresin was identified as Pennzoil Resin 2800. This was a black viscousmaterial having a viscosity of about 2800 SUS at 210 F. A quantity ofthis resin was treated with 1.4 wt. percent of sodium in the followingmanner. A dispersion consisting of 90 wt. percent of the quench oil basestock described below and 10 wt. percent of sodium was prepared byplacing the base stock in a Manton-Gaulin homogenizer and heating it tothe melting point of sodium, i.e. about 98-100 C., then dropping thesodium in the form of thumbnail-size lumps into the heated oil andcirculating the mixture through the homogenizer. Then a portion of theresulting dispersion was reacted with the resin in a proportioncalculated to react 1.4 wt. percent of sodium with the resin. Thisreaction was run at 300 F. for 2 hours. The sodium treated resin wasthen blended into additional quench oil base stock to make a quench oilcomposition. The quench oil base stock consisted of about equal volumesof a 72 V1. refined lubricating oil of 34 SUS viscosity at 210 F. and a77 VI. parafiinic base stock of 39 SUS viscosity at 210 F. The completedquench oil composition consisted of 5 wt. percent of the sodium treatedresin and 95 wt. percent of the quench oil base stock.

For comparative purposes a similar quench oil was prepared using 95 wt.percent of the same base stock and 5 wt. percent of the untreatedPennzoil Resin 2800. The quenching power of each of the quench oils wasevaluated using the General Motors Magnetic Quenchometer. The GeneralMotors Magnetic Quenchometer test takes advantage of the fact that somemetals lose their magnetism when heated above a critical temperatureknown as the Curie point and regain magnetism when cooled below thecritical temperature. High purity nickel with 'a Curie point of about670 F. is ordinarily used in this test as the metal because of itsnon-scaling characteristics and its resistance to cracking upon repeatedheating and cooling. A spherical nickel specimen having a diameter ofinch and weighing about 50 grams is used in these tests and the surfaceof the nickel balls is protected from the oxidizing atmosphere with asurface layer of diffused chromium. The nickel sphere is heated to 1550F. and then plunged into 200 cc. of the quench medium being used, thequench medium being surrounded by a magnetic field. The temperature ofthe quench oil is initially 140 F. A special timing device determinesthe quenching TABLE I Oil tested: Quench time (seconds) Base oil 22.5Base oil 5% resin (untreated) 14.2 Base oil 5% sodium-treated resin 11.5

It will be noted from the data that the base oil had a quench time of 22to 23 seconds, which is too slow for many purposes. The petroleum resinreduced the quenching time to 14.2 seconds. Treating the resin withsodium caused a further reduction in quenching speed to 11.5 seconds.Thus, by employing the present invention there was a decided improvementin quenching speed as compared to the prior art composition.

Example 2 (comparative example) A quench oil was prepared by blending 5wt. percent of an asphalt having a softening point of 130 F. with wt.percent of the same base oil used in Example 1. A second quench oil wasprepared by using instead of the asphalt itself an equal amount of thesame asphalt that had been treated with sodium in the same manner thatthe petroleum resin of Example 1 was treated with sodium. These twoblends were subjected to the quenchometer test described in Example 1.Both of the blends have quenching speeds of from 11 to 12 seconds. Thus,treating the asphalt with sodium gave no measurable change in quenchingspeed. Although it would thus seem that the quench oils containingasphalt would be equally as good as quench oils prepared in accordancewith the present invention, quench oils prepared with asphalt have aserious disadvantage because of a tendency to oxidize and form sludge.Thus, the present invention provides a quench oil having a quenchingspeed as good as that of a quench oil prepared with asphalt which at thesame time overcomes some of the disadvantages of the latter type ofquench oil (See US. Pat. 3,205,100.)

Although this invention has been described in the preferred embodimentswith a certain degree of particularity, it will be understood that thereis no intention to limit the invention to the specific examples, asnumerous modifica tions and adaptations thereof can be resorted towithout departing from the spirit and scope of the invention as definedby the appended claims.

What is claimed is: 1. A quench oil composition comprising a majorproportion of a hydrocarbon lubricating oil having a viscosity withinthe range of about 50 to 2000 SUS at F. to which has been added fromabout 0.3 to 10 weight percent of an alkali-metal-containing additive,

said additive being the result of adding from about 0.2

to 5 Weight percent of an alkali metal to a petroleum resin and heatingthe mixture to a temperature of from about 250 to 450 F.,

said petroleum resin being obtained by light hydrocarboln treatment ofthe residuum of a parafiinic crude o1 2. Quench oil composition asdefined by claim 1 wherein said additive is the result of adding about0.3 to 3 weight percent of sodium to said resin.

3. Quench oil composition as defined by claim 1 wherein said alkalimetal is sodium.

4. Quench oil composition as defined by claim 1 wherein said resin has aviscosity in the range of from about 1000 to 10,000 SUS at 210 F.

5. In a method of quenching that is useful in the treatment of metalswherein a metal to be treated is heated to an elevated temperature andwherein said heated metal is then rapidly quenched in a quenching mediumto bring about desired metallurgical changes in said metal, theimprovement which comprises using as said quenching medium a liquidcomposition as defined by claim 1.

References Cited UNITED STATES PATENTS 2,340,726 2/1944 Horst et a1.148-18 2,600,290 6/1952 Corneil 148-28 X 2,967,816 1/1961 Hudson 208-443,027,315 3/1962 Rodman et al. 148-29 X 3,224,910 12/1965 McEWen 148-28X 3,489,619 1/1970 Brewster 148-18 X 3,567,640 3/1971 Stroh 148-29 XFOREIGN PATENTS 1,495,862 8/1967 France 148-28 L. DEWAYNE RUTLEDGE,Primary Examiner 10 G. K. WHITE, Assistant Examiner US. Cl. X.R.

